FLU NEWS SCAN: China unlikely 2009 H1N1 source, human flu challenge

Jul 28, 2011

Study finds no evidence of China origin for 2009 H1N1 virus
Scientists have suspected that the 2009 H1N1 virus may have originated in China, given that country's large human and pig populations and the fact that is the only known area where American triple-reassortant (TR) and Eurasian (EA) lineage swine flu viruses coexist. However, a gene study of viruses isolated in Hong Kong and Guangdong province swine before and after the pandemic found no evidence that it originated in China, according to a study published yesterday in the Journal of Virology. The research group included researchers from China, Hong Kong, and the United States. They examined the genome sequences of 405 swine influenza viruses from China. Then they conducted phylogenetic analyses that allowed them to group the viruses by host-specific lineages, which fell into eight distinct genotype patterns. The TR-EA reassortants they found all arose from independent events, suggesting they were transient events that may have been confined to a small swine population. None of the viruses had an identical genotype to the 2009 H1N1 virus. The group suggested that lack of persistence in the reassortants could mean the viruses lack pandemic virus characteristics or that the gene segments aren't compatible enough to produce a stable virus.
Jul 27 J Virol abstract

Experts suggest model for conducting human flu challenge studies
Members of an influenza transmission strategy group of the United Kingdom Clinical Research Collaboration made the case for more human challenge studies to help researchers better understand disease dynamics and design better flu prevention interventions. Their discussion appears in a Personal View piece in the Jul 26 issue of Lancet Infectious Diseases. The group described the history of human challenge studies, detailed recent findings, and weighed the advantages and disadvantages of three different challenge study models: exposing volunteers to naturally infected patients, artificially inoculating subjects with a research strain, and exposing deliberately infected volunteers to other volunteers. They conducted a small trial of the third option, exposing nine inoculated (H3N2) volunteers to 15 seronegative subjects. Five donors (inoculated individuals) got sick, and seven of them had confirmed infections. Five recipients (previously seronegative subjects) got sick, of whom three had confirmed infections. Researchers determined that the attack rate was 25%. No adverse events were reported. They suggested that the research model they used needs refinement but could be used to confront key questions about flu transmission.
Jul 26 Lancet Infect Dis abstract

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